1. Field of the Invention
The present invention relates generally to implantable medical devices, and more specifically relates to electrical sensing leads for medical applications.
2. Description of the Prior Art
A number of inventors have taught systems which have multiply displaced electrodes. Typically, these electrodes are used for both stimulation and sensing. However, notwithstanding the displacement of multiple electrodes, these references appear not to teach displacing electrodes about three mutually orthogonal axes for the purposes of measuring current vectors in three dimensional space. U.S. Pat. No. 4,154,247 issued to O'Neill, teaches the use of multiply spaced electrodes. FIG. 4f, for example, teaches the use of three electrodes. However, it is assumed from the teaching of O'Neill that the embodiment pictured in FIG. 4f uses electrodes 612 and 615 connected to a single conductor, making them electrically equivalent. The result is simply a bipolar lead with the sensing capability located within a plane rather than in a line as with most bipolar leads.
The European Patent Office Publication No. 0,009,734 issued to Babotai discloses a lead having electrodes dispersed over more than one axis. As with the teaching of O'Neill these electrodes are directed primarily to stimulation rather than sensing. Furthermore, because the electrodes do not emanate from a single cylindrical lead body, the exact positional representation of currents sensed by these electrodes is extremely difficult to determine.